the fundamental purpose of this project is to investigate the single and combined effects of aging and training on blood pressure responses of male and female hypertensive rats. Long-term studies (1.8 - 2.0 years) currently underway pertain to resting caudal artery blood pressure, sub-maximal and maximal oxygen consumptions, and wall-lumen ratios in caudal arteries. The availability of a custom-made rat treadmill allows us to use a standardized stress test to evaluate the effects of age, weight, sex, training, disease, and therapy on aerobic functional capacity. It also allows us to monitor and to adjust the exercise program to the ability of the animal. In the year ahead we plan to initiate similar studies with younger (15 days old) and older (365 days old) animals. Since it is unlikely that training alone can normalize resting pressures in SHR groups, projects will be undertaken concerned with the effects of activity and antihypertensive drugs. Coupled with these studies will be experiments concerned with sensitivity changes in chemoreceptors and baroreceptors, temperature regulation, and sino-aortic denervation. We are hopeful that emerging from these investigations will be new information and insights on exercise mechanisms.